The Trek Fuel EX 9.9 is a classic in the trail bike segment. Last year, Trek completely redesigned the bike, putting a storage compartment in the down tube, updating the geometry and revising the suspension. We’ll tell you whether the new Fuel EX can build on the success of its predecessor.

Click here for an overview of the best trail bike in test.

Trek Fuel EX 9.9 X01 AXS Project ONE | 29″ | 140/130 mm | 13.08 kg | € 9,099 | manufacturer website

If you’ve got a big enough budget, you can create your very own Fuel EX dream bike thanks to Trek’s Project One program. The customisation available for the paint job is almost limitless and there are some very fancy finishes to choose from. Our favourite is undoubtedly the ICON/Refliptive option. Trek have increased the travel of the Fuel EX and the 29er now offers 140 mm up front and 130 mm on the rear. The latter is controlled by a FOX 36 Factory fork with a GRIP2 damper and a specially developed RockShox Deluxe RT3 shock with RE:aktiv damping and Thru Shaft technology. The shock design, exclusive to Trek, sees the whole piston rod move through the body of the shock when compressed, making an IFP (internal floating piston) to compensate for volume changes when the shock compresses unnecessary. Without the additional seals of an IFP, which add friction, the shock should respond more sensitively and react more quickly to impacts. The rest of the componentry of the € 9,099 Project One bike leaves little to be desired. The SRAM AXS components and Shimano XTR four-piston brakes are tried and tested. The only two things we would have changed are a longer dropper post to replace the standard 150 mm version and grippier tires. The 2.6” Bontrager XR4 tires couldn’t convince us and should be swapped before you leave the shop. We were also annoyed by the chain constantly slapping the chainstay when riding in a hard gear.

Trek Fuel EX 9.9 X01 AXS Project ONE

€ 9,099


Fork FOX 36 FLOAT Factory GRIP2
Rear Shock FOX Float RE:aktiv Thru Shaft
Seatpost RockShox Reverb AXS 150 mm
Brakes Shimano XTR M9120 (Serie XT) 200/180 mm
Drivetrain SRAM X01 Eagle AXS 32/10-50
Stem Bontrager Line Pro 50
Handlebar Bontrager Line Pro 780 mm
Wheelset Bontrager Carbon 30
Tires Bontrager XR4-Team Issue 120 TPI 120 2,6

Technical Data

Size XS S M L XL
Weight 13,08 kg
Wheelsize 29"
Travel (f/r) 140/130 mm

Firm and direct
Despite complex technology in the shock, the rear end of the Fuel EX isn’t the plushest or most sensitive. Instead, it’s rather firm and defined
The Bontrager XR4 Team Issue tires couldn’t deliver. They offer little grip and slide uncontrollably over the entire tread. We would recommend fitting something with more aggressive shoulder knobs.
Excellent choice
Up until a few years ago, a 140 mm trail bike would have come with a FOX 34 fork. It is all the better to see that Trek have chosen to fit a FOX 36 with a GRIP2 damper – excellent!
Practical, but small
The storage compartment in the down tube on the Trek offers space for a tube and tools and is super easy to open. Unfortunately, the opening is very small – compared to Specialized’s SWAT box, getting stuff in and out is a fumble.
We didn’t use the flip chip and although the steeper seat tube angle would have been nice on the climbs, we preferred the slacker setting for the descents. In practice, changing it back and forth is too much of a hassle.
Top class
The paint effect combined with matt black elements is just one of many possibilities with Trek’s Project One configurator

Geometry of the Trek Fuel EX 9.9

Trek have never been known for extreme geometry and the Fuel EX doesn’t buck that trend. The 470 mm reach in size L is just right, the head angle is not particularly slack at 66° and the 75° seat tube angle is rather conservative. On top of that, the effective seat tube angle slackensas you extend the dropper post due to the bend in the seat tube. Like the Slash, the Fuel EX features the Mino Link flip chip to adjust the geometry, but we always left it in the slacker setting.

With Trek’s Project One program, there are almost no limits to your own creativity – if you’re dreaming of a custom paint job, this is what you need!

Size XS 27,5″ S 27,5″ S 29″ M 29″ ML 29″ L 29″ XL 29″ XXL 29″
Seat tube 356 mm 395 mm 395 mm 420 mm 435 mm 450 mm 500 mm 540 mm
Top tube 546 mm 568 mm 578 mm 603 mm 619 mm 634 mm 663 mm 688 mm
Head tube 90 mm 100 mm 100 mm 100 mm 105 mm 105 mm 105 mm 140 mm
Head angle 66° 66° 66° 66° 66° 66° 66° 66°
Seat angle 75° 75° 75° 75° 75° 75° 75° 75°
Chainstays 437 mm 437 mm 437 mm 437 mm 437 mm 437 mm 437 mm 437 mm
BB–Offset 43 mm 43 mm 43 mm 43 mm 43 mm 43 mm 43 mm 43 mm
Wheelbase 1.120 mm 1.144 mm 1.154 mm 1.179 mm 1.196 mm 1.211 mm 1.242 mm 1.270 mm
Reach 395 mm 415 mm 415 mm 440 mm 455 mm 470 mm 495 mm 515 mm
Stack 563 mm 572 mm 608 mm 608 mm 613 mm 613 mm 627 mm 645 mm

The Fuel EX on test

The Fuel EX gives you that typical Trek feeling right from the start. The riding position is slightly stretched due to the slack seat tube angle and the front is low. This is perfect for going fast on level terrain. However, you should push the saddle forward if you’re going to tackle steep climbs. Thanks to the firm suspension and light wheels, the Fuel EX accelerates very willingly and conserves your energy on long rides. Light-footed as it is, the bike masters technical climbs with ease, but the Bontrager tires lack grip on wet roots.

The Fuel EX is a super versatile bike – efficient on the climbs and balanced on the descents!

The tires also leave the bike struggling on the descents. As this put it far behind the competition, we tested the Fuel EX with different tires fitted. The position on the bike is central and the handling is super intuitive. This makes the Trek an easy bike to ride fast. Changing direction is quick and easy and the bike motivates you to manual or catch air as soon as you hit a roller or lip. The agile handling only becomes a disadvantage in really rough terrain where it takes a strong rider to keep the bike on course. At high speeds, the firm suspension doesn’t help here either and despite the Thru Shaft technology in the shock, the rear doesn’t respond as sensitively as the best bikes in the test.

Tuning tip: swap the tires | push the saddle forward | better chainstay protector

Helmet 100% Altec | Glasses Oakley Jawbreaker | Shirt Fox Ranger | Short Short POC Resistance Enduro Light Shorts | Kneepads Fox Launch Pro | Hip Bag USWE Zulo 2l

How does the Fuel EX compare to the competition?

The firm character of the Trek Fuel EX is not unlike the Norco Optic C1, though the Trek does offer more comfort overall. Aggressive riders are better off with the Norco due to the added support of the suspension and more progressive geometry. Relaxed riders, on the other hand, will find a more versatile and good-natured bike in the Trek.

Riding Characteristics



  1. sluggish
  2. efficient


  1. cumbersome
  2. playful


  1. nervous
  2. confident


  1. demanding
  2. balanced


  1. harsh
  2. plush

Fun Factor

  1. planted
  2. poppy

Value for money

  1. terrible
  2. very good

Intended Use









Conclusion of the Trek Fuel EX

The Trek Fuel EX is a great all-rounder that offers very intuitive and good-natured handling. It’s a very efficient and playful bike, but it lacks composure in demanding terrain. If you’re looking for one bike to do it all, this is it – as long as you fit different tires.


  • light-footed and efficient climber
  • intuitive, good-natured and fun handling
  • storage compartment in the down tube for tools or food


  • not the most sensitive rear end
  • tires lack grip
  • chain slap

For more information head to

The test field

Click here for an overview of the best trail bike in test.

All bikes in review: Cannondale Habit Carbon 1 (Click for review) | Canyon Spectral CFR 9.0 SL (Click for review) | Giant Trance Advanced Pro 29 (Click for review) | Ibis Ripmo AXS (Click for review) | Nukeproof Reactor 290 (Click for review) | Norco Optic C1 (Click for review) | Orbea Occam M-LTD (Click for review) | Radon Slide Trail 10 (Click for review) | Santa Cruz Hightower CC X01 Reserve (Click for review) | Scott Genius 900 Tuned AXS (Click for review) | Specialized Levo SL Expert Carbon (Click for review) | Specialized S-Works Stumpjumper SRAM AXS 29 (Click for review) | Yeti SB130 TLR (Click for review) | YT JEFFSY CF PRO (Click for review)

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Words: Photos: Christoph Bayer, Finlay Anderson, Markus Frühmann, Jonas Müssig